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Low cost high tech crop scouting with handheld GPS

Editor’s note: This article is from the archives of the MSUCrop Advisory Team
Alerts. Check the label of any pesticide referenced to ensure your use is
included.

Advances
in handheld global positioning system (GPS) receivers provide growers
with a low cost tool for crop scouting. A satellite based augmentation
system has been developed by the government for the aviation industry to
improve the accuracy and integrity of information signals broadcast by
GPS satellites. This technology is driving down the price and increasing
the accuracy of handheld GPS receivers. The primary commercial market
for these low cost handheld units is for travel and recreational
navigation. However, the technology has many practical applications in
crop scouting.

Global positioning systems are not new to agriculture. In fact, they are
custom equipment on most combines and large tractors. To achieve the
level of precision needed for most agricultural applications, these
units typically relied on land-based differential correction signals in
addition to the GPS satellite signals. These land-based correction
signals are available from several sources including the U.S. Coast
Guard beacons, and pay-to-use subscription services. The correction
signal, antennae requirements, and correction factor software
contributed to the relatively high price of these GPS units.

The U.S. Federal Aviation Administration and Department of
Transportation developed a satellite-based correction system called WAAS
for “wide area augmentation system.” WAAS uses a system of
approximately 25 ground-based reference stations, which monitor GPS
satellite data. Two primary stations located on each coast, receive data
from the reference stations and calculate a GPS correction signal,
which accounts for GPS satellite signal errors from ionospheric
disturbances, timing and satellite orbit errors. The correction signal
is then broadcast through one of two satellites with a fixed orbit over
the equator. The correction signal is compatible with the basic GPS
signal structure and is able to be picked up free of charge by any WAAS
enabled receiver. Initial WAAS testing, confirmed performance accuracy
of three to six feet horizontal and six to nine feet vertical throughout
the majority of the continental United States. Handheld GPS units
equipped to use the WAAS signal are currently commercially available in
the $200 range and are available at most sporting goods and outfitting
stores.

How can these handheld GPS units be used in crop scouting? Many
applications are possible, and given farmer ingenuity, many new uses
will likely evolve over the next few years. The devices can be used to
accurately identify the location of insect, disease, weed, nutrient, pH,
tile blow-outs and other soil problems in the field observed while
scouting. Once the problem areas are marked and electronically stored in
the device’s memory, the unit can be used to navigate back to them
later on for corrective action. The ability to navigate back to
identified trouble spots makes this technology ideal for monitoring the
effectiveness of applied treatments, whether they be pesticides,
fertilizers or pH adjustments. In addition to marking and navigating,
many of these handheld units have the capability to measure distances
and even calculate acreage. Since the units measure elevation in
addition to lateral position, they can also be used to determine surface
drainage patterns. Most units also have a limited memory, which can be
used to store shape-files of fields. The possibilities are endless, but
perhaps best of all, once the field work is done, you can use the same
unit to mark and navigate to your favorite fishing and hunting hotspots.

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